<?php

/*

 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between

 * diffiehellman.php - Diffie Hellman key exchange and supporting functions

 *

 * This program is Free Software; you can redistribute and/or modify it under the terms of the GNU General Public License

 * as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied

 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.

 */

/**

 * EnanoMath GMP backend

 */

class EnanoMath_GMP

{

  var $api = 'GMP';

  /**

   * Initializes a number to a GMP integer.

   * @param string String representation of the number

   * @param int Base the number is currently in, defaults to 10

   * @return resource

   */

  function init($int, $base = 10)

  {

    return ( is_resource($int) ) ? $int : gmp_init($int, $base);

  }

  /**

   * Converts a number from a GMP integer to a string

   * @param resource

   * @param int Base, default is 10

   * @return string

   */

  function str($int, $base = 10)

  {

    return ( is_string($int) ) ? $int : gmp_strval($int, $base);

  }

  /**

   * Converts a number between bases.

   * @param resource BigInt to convert

   * @param int Base to convert from

   * @param int Base to convert to

   */

  function basecon($int, $from, $to)

  {

    return $this->init(gmp_strval(gmp_init($this->str($int), $from), $to));

  }

  /**

   * Generates a random integer.

   * @param int Length

   * @return resource

   */

  function random($len)

  {

    return gmp_random($len / 8);

  }

  /**

   * Powmod operation (calculates (a ^ b) mod m)

   * @param resource a

   * @param resource b

   * @param resource m

   * @return resource

   */

  function powmod($a, $b, $m)

  {

    $a = $this->init($a);

    $b = $this->init($b);

    $m = $this->init($m);

    return ( function_exists('gmp_powm') ) ? gmp_powm($a, $b, $m) : gmp_mod(gmp_pow($a, $b), $m);

  }

}

/**

 * EnanoMath big_int backend

 */

class EnanoMath_BigInt

{

  var $api = 'big_int';

  /**

   * Initializes a number to a BigInt integer.

   * @param string String representation of the number

   * @param int Base the number is in, defaults to 10

   * @return resource

   */

  function init($int, $base = 10)

  {

    return (is_resource($int)) ? $int : bi_from_str($int, $base);

  }

  /**

   * Converts a number from a BigInt integer to a string

   * @param resource

   * @param int Base, default is 10

   * @return string

   */

  function str($int, $base = 10)

  {

    return ( is_string($int) ) ? $int : bi_to_str($int, $base);

  }

  /**

   * Generates a random integer

   * @param int Length (bits)

   * @return resource

   */

  function random($len)

  {

    return bi_rand($len);

  }

  /**

   * Converts a number between bases.

   * @param resource BigInt to convert

   * @param int Base to convert from

   * @param int Base to convert to

   */

  function basecon($int, $from, $to)

  {

    return bi_base_convert($this->str($int, $from), $from, $to);

  }

  /**

   * Powmod operation (calculates (a ^ b) mod m)

   * @param resource a

   * @param resource b

   * @param resource m

   * @return resource

   */

  function powmod($a, $b, $m)

  {

    $a = $this->init($a);

    $b = $this->init($b);

    $m = $this->init($m);

    return bi_powmod($a, $b, $m);

  }

}

/**

 * EnanoMath BCMath backend

 */

class EnanoMath_BCMath

{

  var $api = 'BCMath';

  /**

   * Initializes a number to a BCMath integer.

   * @param string String representation of the number

   * @param int Base the number is in, defaults to 10

   * @return resource

   */

  function init($int, $base = 10)

  {

    return $this->basecon($int, $base, 10);

  }

  /**

   * Converts a number from a BCMath integer to a string

   * @param resource

   * @param int Base, default is 10

   * @return string

   */

  function str($res)

  {

    return ( is_string($res) ) ? $res : strval($this->basecon($res, 10, $base));

  }

  /**

   * Generates a random integer

   * @param int Length in bits

   * @return resource

   */

  function random($len)

  {

    $len = 4 * $len;

    $chars = '0123456789abcdef';

    $ret = '';

    for ( $i = 0; $i < $len; $i++ )

    {

      $chid = mt_rand ( 0, strlen($chars) - 1 );

      $chr = $chars{$chid};

      $ret .= $chr;

    }

    return $this->basecon($this->init($ret), 16, 10);

  }

  /**

   * Converts a number between bases.

   * @param resource BigInt to convert

   * @param int Base to convert from

   * @param int Base to convert to

   */

  function basecon($int, $from, $to)

  {

    if ( $from != 10 )

      $int = $this->_bcmath_base2dec($int, $from);

    if ( $to != 10 )

      $int = $this->_bcmath_dec2base($int, $to);

    return $int;

  }

  /**

   * Powmod operation (calculates (a ^ b) mod m)

   * @param resource a

   * @param resource b

   * @param resource m

   * @return resource

   */

  function powmod($a, $b, $m)

  {

    $a = $this->init($a);

    $b = $this->init($b);

    $m = $this->init($m);

    return ( function_exists('bcpowmod') ) ? bcpowmod($a, $b, $m) : bcmod( bcpow($a, $b), $m );

  }

  // from us.php.net/bc:

  // convert a decimal value to any other base value

  function _bcmath_dec2base($dec,$base,$digits=FALSE) {

      if($base<2 or $base>256) die("Invalid Base: ".$base);

      bcscale(0);

      $value="";

      if(!$digits) $digits=$this->_bcmath_digits($base);

      while($dec>$base-1) {

          $rest=bcmod($dec,$base);

          $dec=bcdiv($dec,$base);

          $value=$digits[$rest].$value;

      }

      $value=$digits[intval($dec)].$value;

      return (string) $value;

  }

  // convert another base value to its decimal value

  function _bcmath_base2dec($value,$base,$digits=FALSE) {

      if($base<2 or $base>256) die("Invalid Base: ".$base);

      bcscale(0);

      if($base<37) $value=strtolower($value);

      if(!$digits) $digits=$this->_bcmath_digits($base);

      $size=strlen($value);

      $dec="0";

      for($loop=0;$loop<$size;$loop++) {

          $element=strpos($digits,$value[$loop]);

          $power=bcpow($base,$size-$loop-1);

          $dec=bcadd($dec,bcmul($element,$power));

      }

      return (string) $dec;

  }

  function _bcmath_digits($base) {

      if($base>64) {

          $digits="";

          for($loop=0;$loop<256;$loop++) {

              $digits.=chr($loop);

          }

      } else {

          $digits ="0123456789abcdefghijklmnopqrstuvwxyz";

          $digits.="ABCDEFGHIJKLMNOPQRSTUVWXYZ-_";

      }

      $digits=substr($digits,0,$base);

      return (string) $digits;

  }

}

/**

 * Creates a new math object based on what libraries are available.

 * @return object

 */

function enanomath_create()

{

  if ( function_exists('gmp_init') )

    return new EnanoMath_GMP();

  else if ( function_exists('bi_from_str') )

    return new EnanoMath_BigInt();

  else if ( function_exists('bcadd') )

    return new EnanoMath_BCMath();

  else

    throw new Exception('dh_err_not_supported');

}

?>